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参数资料
| 型号： | A3998SETTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 9/20页 |
| 文件大小： | 0K |
| 描述： | IC MOTOR DRIVER DUAL DMOS QFN |
| 标准包装： | 1 |
| 应用： | 直流电机驱动器，PWM 电机驱动器，步进电机驱动器 |
| 输出数： | 1 或 2 |
| 电流 - 输出： | ±1.5A |
| 电压 - 负载： | 9 V ~ 50 V |
| 电源电压： | 3 V ~ 5.5 V |
| 工作温度： | -20°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-VFQFN 裸露焊盘 |
| 供应商设备封装： | 32-QFN |
| 包装： | 标准包装 |
| 其它名称： | 620-1459-6 |
A3998
Configuration Register
A configuration register supporting four 16-bit words can be set
using the serial port.
Dual DMOS Full Bridge Motor Driver
With Serial Port Control and Dual Regulators
Five bits (word 0/1, D6:D2) are available for each full bridge
to adjust the fixed off-time, t OFF , when Internal PWM current
control mode is selected.
The Configuration register is volatile memory accessed through
the serial port. The bit descriptions are shown in table 1. At a
power-on reset (POR), the bits are set to their default values, all
The off-time is defined by the following equation:
t OFF = (1 + N ) × T OSC × 8 – T OSC
(3)
zeros with the exception of the MSB of the fixed off-time param-
eters, which are set to one.
Motor Driver
Full Bridge Output Current Regulation
Maximum load current is regulated by an Internal PWM mode,
fixed off-time current control circuit. When the outputs of the
DMOS full bridges are turned on, current increases in the motor
winding until it reaches a value given by:
where N is the word value, from 0 to 31, and T OSC is the period
of the internal oscillator.
For example, given the internal oscillator frequency, f OSC , of
4 MHz (typ) (T OSC = 250 ns), the fixed off-time is adjustable
from 2 to 64 μ s in increments of 2 μ s.
PWM Control Mode
The selection of Internal or External PWM control mode for each
full bridge is made in the Configuration register.
? Selection of Internal control mode (word 2, D0 and D7) sets
I TRIP = V REF × Current Ratio / (5 × R S )
(2)
the Internal PWM Decay Mode (Mixed or Slow), and allows
where R S is the value of the sense resistor RS, and the Current
Ratio is as shown in table 2.
At the trip point, the sense comparator resets the source enable
latch, turning off the source driver. At this point, load inductance
causes the current to recirculate for the serial port programmed
fixed off-time period. The current path during recirculation is
determined by the configuration of slow/mixed decay mode and
the synchronous rectification control bits.
Fixed Off-Time
The PWM timer is programmable via the serial port to provide
fixed off-time PWM signals to the A3998 internal control block.
the configuration of Fixed Off-Time and Fast Decay Time. In
Mixed Decay mode, during the first portion of the off-time
period, the A3998 operates in Fast Decay mode, until the Fast
Decay time count is reached. The rest of the fixed off-time pe-
riod the A3998 operates in Slow Decay mode. If the Fast Decay
Time duration is longer than the Fixed Off-Time duration, the
device effectively operates in Fast Decay mode throughout the
period.
? Selection of External control mode (word 2, D1 and D8) sets
the External PWM Decay Mode (Fast or Slow). In this mode, a
chopping signal on the Enable pins (ENBx) are used to provide
external PWM current control.
STB
C
D
E
F
CLK
DATA
SLEEPN
H
A
MSB
B
LSB - D0
G
A.
B.
C.
D.
Minimum Data Setup Time
Minimum Data Hold Time
Minimum Setup Strobe to Clock Rising Edge
Minimum Clock High Pulse Width
15 ns
10 ns
50 ns
50 ns
E.
F.
G.
H.
Minimum Clock Low Pulse Width 50 ns
Minimum Setup Clock Rising Edge to Strobe 50 ns
Minimum Strobe Pulse Width 50 ns
Minimum Sleep to Clock Setup Time 100 ns
Figure 4. Serial Port Timing Diagram
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
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